Long hours of driving cause the driver's tissue at the thighs and hips to be pressurized for an extended period and result in considerable discomfort and driver fatigue. Capillary blood vessels may collapse under a pressure higher than 30 mmHg thereby interfering with blood perfusion and circulation when the driver is seated for a long time. Furthermore, continuous contact with the seat surface often causes heat and moisture accumulation at the contact surface. Periodically stimulating the tissue in contact with the car seat, as well as providing adequate ventilation and pressure relief may alleviate these problems. Automotive manufacturers are enhancing the value of luxury cars by adding more functionality to the car seats.
These car seats are instrumental in providing a relaxed and comfortable driving experience, especially during long trips. Heated car seats are available in many cars, and systems that have cooling as well as heating of the seat surface have also been developed. Embedding a massage function in car seats is another new feature that is gaining popularity.
A driver who is driving for an extended period of time can be fatigued due to inadequate blood perfusion at the tissue under persistent pressure. Stimulation of the tissue as well as pressure relief and ventilation, are desirable. This can reduce the fatigue of the driver, thereby reducing the risk of accidents caused by driver's fatigue. This can generally be accomplished by massage. However, the massage effect should not interfere with driving and, therefore, conventional massage is not generally applicable to driving an automobile.
There are three types of active car seats providing massage effects. One is a vibrating and kneading massage cushion for car seats. These are built with simple DC motors with eccentric weights in order to create vibration. Due to the nature of the DC motor, the frequency of the vibration is high, creating a rapid vibratory motion. But these fast vibrations could cause itchiness and other discomfort when applied for a long time.
Therapeutic massage chairs similar to home-use massagers have been applied to back seats and passenger side seats. These may interfere with driving, and are therefore not applicable to driver car seats. Bulky motors and mechanisms also make them unfavorable for car seat applications.
There is another type of massage car seat that uses air inflation to create bumps on the surface of the seat. The bumps created by air inflation are limited to a simple round shape. They are effective for redistributing pressure, but no sophisticated motion can be created.